1. The Field of the Invention
The present invention is directed generally to grounding clips, and in particular, to grounding clips for solar panels.
2. Background Art
Recent advancements in solar cell technology and skyrocketing fossil fuel prices have prompted many businesses to consider solar energy as an alternative energy source. Many commercial buildings have flat roofs. These large expanses of flat spaces present ideal opportunities to place solar panels as they are typically not publicly accessible and free from significant natural debris such as leaves or shade cast by trees or buildings.
As labor costs are high, it is imperative to resort to a solar racking system having a grounding system that is simple to install, one that does not require highly trained professionals to be present at all times. For example, installation costs can be reduced if the electrician is only required to be present only when solar panels are ready to be electrically enabled.
The present ground clip has been devised for use in installing a solar panel array composed of multiple photovoltaic or solar panels that are assembled onto a racking system. The frames of solar panels are generally fabricated from aluminum and the racking system on which the solar panels are mounted are generally fabricated from steel or aluminum. If Aluminum is used, it is anodized to resist corrosion. If steel is used, Galvalume® and/or powder coating may be applied to prevent corrosion. As in any source of electrical power, to ensure safety, any racking system and solar panel frames must be electrically bonded together. As used herein, the term “bonded” means permanently joined to form an electrically conductive path that ensures electrical continuity and has the capacity to safely conduct any current likely to be imposed. Although the frames of the solar panels are directly clamped to a racking system or otherwise in abutting contact with the racking system, the anodizing of the frames insulates the frames and the racking system so that they are not electrically connected together.
A common practice in the industry is to install a separate grounding lug on each solar panel and running a ground wire from panel to panel. The grounding lug is attached to the extruded aluminum frame of the solar panels with a thread forming stainless steel screw. As the screw cuts into the aluminum, it forms an air-tight connection which will maintain good electrical connection over time. A common sheet metal thickness is 0.080 inch (2 mm) and a common screw size is 10-32. The screw therefore only makes connection on about 2.5 threads. This gives a marginally acceptable surface contact area in terms of mechanical strength and electrical conductivity. It would be desirable to have a design where the electrical contact area can be made much larger.
In a conventional grounding setup, a stainless steel screw contacts a star washer which in turn contacts the grounding lug body. The grounding lug accepts a copper wire which is forced to contact the grounding lug by a stainless steel set screw. In some occasions, the copper wire could also be crimped to the lug. There are thus four connection points which must be made, i.e., sheet metal to screw, screw to star washer, star washer to lug, and lug to copper wire. It would be desirable to have a design where there are only two electrical connection points when electrically bonding two objects to reduce installation time, risk and effort.
Copper wire is strung between grounding lugs on all the solar panels and eventually to a ground electrode. The grounding lugs themselves are expensive and time consuming to install and the wiring adds both material and labor cost which increase the price of the overall system. It would be preferable if the electrical connection was made directly between the metal pieces when they are assembled together.
Given these concerns, several solar panel support systems have been designed to solve some of these problems. However, none of the prior art systems are designed to capable of addressing all of these concerns.
U.S. Pat. No. 8,092,129 to Wiley et al. discloses a bonding washer for making electrical connection between two metal pieces that are to be mechanically fastened together. The washer, to be interposed between the solar panel and mounting system, is constructed so as to fasten to one of the pieces before the two pieces are joined. Teeth on the washer, positioned at right angles to the plane of the washer, are forced into each of the two metal pieces when the fastener is tightened, making electrical connection between solar panel and mounting rail. This patent discloses a washer capable of electrically ground only two metal pieces. Although the washers of the '129 patent appear superior as compared to conventional grounding practices using grounding lugs, they are limited in their ability to reduce the number of grounding clips required to ground a racking system and the solar panels mounted on the racking system.
Thus, there arises a need for a solar panel grounding system which is simple in construction and installation, one that does not require regular maintenance, one that provides superior grounding to conventional grounding methods and one that does not require modifications to existing flat roofs on which the racking system is used.